


Interesting

by Arixese



Category: Undertale (Video Game)
Genre: Brief dirty talk, Cunnilingus, Desk Sex, F/M, Teasing, Vaginal Sex
Language: English
Status: Completed
Published: 2017-05-16
Updated: 2017-05-16
Packaged: 2018-11-01 09:12:52
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,282
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10918791
Author URL: https://archiveofourown.org/users/Arixese/pseuds/Arixese
Summary: Gaster is a workaholic, but what else is new? All you want is some sleep, but he refuses to join you in bed. For a doctor, he doesn't exactly live a healthy lifestyle. Hell, for all you know,  he could very well collapse from exhaustion at this rate! But, convincing him to retire for the night is no easy task. Luckily, there is one thing that just might work.





	Interesting

You were well aware of the eyes following you around the room. But, you weren't bothered by it, nor did it make you uncomfortable. In fact, you grinned at the attention, but pretended not to notice as you straightened your back and closed the file cabinet with a heavy thunk. A voluminous stack of papers were barely contained in the folder clutched in your arms; perhaps you should spend some time to straighten up when you get the chance, tomorrow.You straightened your back and rubbed your eyes blearily. Gaster never kept a clock in his office, but you were certain that it was somewhere in the early morning at this point. You just stopped by to check up on him, keeping up his continual supply of coffee. But, instead of that, you got roped into playing secretary. And not the sexy kind, much to your disappointment.

“Here's the file you wanted,” you declared as you laid the bundle of papers on his desk. Gaster thanked you briefly before poring over his notes, translating the written words seamlessly from wingding to English. His eyes flickered to you every so often, and his shoulder jumped under your palm when you rested your hands on him, lightly massaging his clavicles. “How are things coming? About ready to retire for the night, dear?”

Gaster shook his head firmly. “Not quite yet. I want to have this done in time for the Ebott Research Facility.” His voice rippled in your ears like an echo, almost otherworldly. Such an entrancing sound. A lot of folks like to hear themselves talk, but you could listen to that all day. But still, you grimaced at the misplaced resolve in his voice.

“Dings, they don't need those notes for another week or so,” you reminded him gently. “Come to bed, dear; I'm afraid of you wearing yourself too thin.”

“Just a bit longer…” In other words: several more hours. Your heart panged with guilt at the prospect of drifting off in bed while your mate wore himself ragged at his desk.

“Aw.” You huffed softly and sank your weight onto his back, draping your arms over his shoulders. “Does that mean I have to go to bed  _ alone _ ?” Gaster’s breath hitched as your hand reached down and curled between his legs. His pen stopped scrawling over the page and trembled slightly in his tensed fingers as you groped at his thighs.

“Dear,” he groaned as one of your hands hiked up his shirt to tug at his spine. “You're not acting f-fairly..” 

“Come to bed,” you reasserted with a purr. “Let me take good care of you. Wouldn't you like that?” Gaster set down his pen and reached backwards towards your cheek and you abandoned feeling up his legs to interlock your fingers. You craned your head to kiss the back of his knuckles before your mouth opened wide. Gaster twitched under you when your tongue curled around his forefingers, and your hand guided him as you sucked on his digits. You hummed around his fingers and the hand stroking his spine wandered downwards, trailing over his zipper. “Wouldn't you like that? Having my mouth around your hard, throbbing cock, sucking you dry? Or, maybe you want me to ride you until you can't take any more?” He stuttered your name helplessly and groped for your hand teasing at his crotch, letting out a small grunt of frustration when you pulled away with a click of your tongue. “Shame your work is  _ so _ important.”

Gaster mumbled harshly under his breath as his fingers snared your wrist with an unyielding grip. You could see the pale flickering white of conjured palms clearing his desk while the former royal scientist stood, his jaw set as he pulled you in by the arm. You grinned at the dark trace of color blooming across his cheekbones like a bruise.

“Sorry, I didn't get that,” you said cheekily, “Is something the matter, Dear?”

Gaster scooped his arm around your back and pulled you forcefully into his chest. His teeth pulled at your earlobe, sending shivers down your spine. “You temptress. You always know just what buttons to push, don't you?” You tingled in pleasure and wrapped your free arm around his shoulders as his hand slid down to grab at your ass. “You have no idea how much I've been trying to restrain myself, tonight,” he mumbled in your ear, fondling and pinching your flesh in his fingers. Both of his hands descended down over the waistband of your pants and groped blindly.

You pushed up onto your toes and planted your lips on his slightly-opened mouth. Gaster hummed as he received you earnestly, pulling you up into him by your thighs. You were lost to vertigo as your legs wrapped around him, deepening your kisses while you felt gravity shift and you grunted as he tipped you over, your back flat against his desk. His hands ghosted under your shirt, pushing the fabric up over your shoulders in a fluid motion. You gripped the desk ledge over your head and watched him right himself over you, discarding his own sweater and light jacket to the ground.

“Taking me right on your desk?” Your eyes skimmed over his ribs and you licked your lips as they landed on the tent forming between his legs. “Dirty boy,” you cooed as your thumbs hooked in your belt loops and shimmied your pants down your thighs. 

“Oh, hush. I know you like it.” Gaster's hands cupped your waist, running up and down your curves and over your stomach. The holes in his palms always added a strange sensation whenever he got to touching you like this, like leaving intense after-images on your skin. Gaster noticed how your hands curled around his forearms, and his eyes shown bright as he watched your back arch off of his desk into him. And, then, his eye caught something, inspiring a dirty chuckle. “ _ Interesting _ ! Perhaps, you're liking it  _ too much _ ? Who's the dirty one, now?” You shuddered as Gaster drew a line up the front of your undies with his finger, parting the growing dampness gathering at your crotch. You felt your clit swell, eager to be touched. Meanwhile, your face flushed considerably with a squeal as Gaster pulled your body closer to the desk edge, slipping your panties off onto the floor. You started when you looked down and saw Gaster lower to his knees before you, and your back spasmed suddenly, your hands gripping the edges of the desk with urgency as you felt something slick flick against your clit. 

You felt Gaster's mouth press to the inside of your thigh as his thumbs gently pulled you apart. “Mmm, my, so wet and responsive, already? You must be so  _ hungry _ for some attention, love. Excuse me while I… reacquaint myself…” His mouth pressed into your mound and lined your labia with small kisses. Your throat quaked with a choked moan as you felt his fingers slide up on either side of his tongue, pulling apart your labia and exposing your clit to his tongue. He began with slow, calculated strokes, the tip of his magicked tongue skimming the surface of your nub running clockwise around you for a moment before eliciting a small gasp and twitch of your thighs as he changed directions.

“F...uuuck…”

“Language, dear.”

You whined as you felt his mouth cup over the top of your slit, his tongue flattening on your nub to cover you in thick, heavy strokes. You chanced a peek down, propping yourself on your elbows to properly see. Your throat caught as you locked eyes with him, his gaze sharp and intense, watching you intently as if not to miss a single detail. He could see your hair beginning to stick to the thin layer of sweat on your skin, your chest heaving with barely stifled gasps and moans, your eyes dilating and contracting wildly with every touch. He ran his tongue over you hard and heavy, pressing down in long strokes, keeping you in the center of his mouth under constant stimulation and watch you work yourself up, before backing of just at the cusp of your orgasm. 

His hands gripped the outside of your thighs as he pulled himself up to his feet. You found yourself collapsed on the desk, your fingers curling over yourself, only to spasm from the sharp ping of overstimulation that flooded your system. “ _ Gasterr… _ ”

Gaster soothed you in shooshing tones as he gently pulled your hand away, bringing it up to kiss the back of your wrist. “You can trust me, dear. I have no intention of leaving you unsatisfied.” The sound of your own voice echoed in the back of your mind as you felt a pair of hands reach under your back and pull you up to sit on the edge of the smooth wooden surface. Your arms latched around his shoulders and you arched your back into his embrace when you felt the shaft of his cock between your legs gliding down to catch on your opening.

“Yes,” you gasped, bucking your ankles around his backside in excitement. “Yes, please!” Gaster clamped his mouth over your shoulder as he pressed inside of you, grunting loudly from the sudden stimulus of your hot, wet core squeezing around his cock. He began slowly, giving himself enough time to adapt to the powerful convulsions of your body, tightening around him and still trembling from your near-orgasm. Meanwhile, you moaned softly with every thrust, and your hands wandered down his spine to grip the back of his hips, urging him to go faster. Gaster's fingers dug into your ass as he quickened his thrusts to match yours. You squeaked suddenly as you felt his cock brush against your g-spot, blinding your vision with a hot-white flash of stars. “There! There! Oh,  _ geesus _ ..!” You leaned back and shifted your hips, groaning as you rolled into the movement. Gaster grunted, his eyes squinted with effort as he concentrated on your rapt expression, noting the angles and force that made your eyes flutter. You were getting lost in the intensity as you fell into his rhythm. Every loud, gasping breath, every hungry groan filled the room as you let the coil in your gut wind in steady waves. You could feel Gaster's cock twitch violently inside you, and his grunts ebbed into low whines. His eyes blacked out with effort and his fingertips started to bruise against your flesh. 

Gaster stuttered your name, chanted it under his breath with every quick, jerky thrust. “O-oh, d-d-damn, I think I… I can't..!” Gaster cried out as he slammed you into his pelvis and you froze as his cock gave a violent spasm, coating your insides in hot, thick ropes of cum. Your own orgasm ripped through you as he shot his load, and Gaster shuddered with a choked cry as your walls slammed shut around him, and your own cum splattered around his dick, coating your thighs. You collapsed your back against the desk when he finally stilled, your chest heaving as you stared blankly at the ceiling. Well, you didn't exactly get him away from his desk, but it was… Something, at least.

You whistled through your teeth. “Yep. That was… certainly  _ something _ ,” You vocalized, earning a weary chuckle from Gaster as he plopped into his desk chair and scooted next to you. He hummed in agreement as he propped his elbow on the desk ledge, interlacing your fingers together in a comforting grasp. He nuzzled the back of your hand, kissing your soft skin as you angled your body to face him. “So.. Bed? Or shower first?” 

Gaster groaned in dismissal. “Ugh… Bed. After such exertion, I simply  _ refuse _ to stay awake a moment longer.”

“You know,” you pointed out, “You’d probably be in better shape if you got some more sleep every now and then.”

“Impossible,” he huffed. “I am already running at the most proficient level of output. My sleep schedule is just fine!” Gaster glared at you with a teasing, petulant glance. But, even though you knew he was trying to be difficult and contrary on purpose, you had difficulty believing he was simply joking. Papyrus was definitely his father’s son in terms of their attitudes towards rest. You reached over and kissed him on the smooth ridge of his brow. 

“Whatever you say, Dear,” you conceded. You pushed yourself off of the wooden desk and grimaced at the sticky residue of sex and sweat on your skin. You didn’t even dare look behind you to see what kind of shape Gaster’s desk was in. “But, uh, a quick rinse-off wouldn’t hurt, right?”

The creak of wood alerted you to Gaster’s presence beside you. He stood pigeon-toed, rubbing at his bones with a distasteful expression on his face. You bet he’d be wrinkling his nose if he had one. “Yyyyyou... have a point. As much as I want to, there’s no way I can fall asleep like this. I feel positively revolting.”

“Then, let’s go ahead and fix that, shall we?” You pecked Gaster on the cheek and grasped his hands, leading him backwards out of the office. Gaster looked you up and down as he followed you out. You gave him a quizzical look, your mouth forming a lopsided grin as you raised an interested eyebrow. “What? Do I have something on my face?” Probably.  You probably have the  _ worst _ sex hair, right now.

“... It just occurred to me…” Gaster sighed and shook his head. His eyes were soft as he smiled at you. “You were right. This was  _ plenty _ more interesting than paperwork.”

**Author's Note:**

> All works 18+. Viewer discretion advised. 
> 
> ATTENTION: I don't post much atm, but I do have a tumblr @arixese if any of y'all wanna send me requests in my ask box.


End file.
